Judge Beryl Howell’s ruling that President Trump’s executive order against the Perkins Coie law firm is unconstitutional is a blow to the 47th president’s efforts to bring Big Law to heel — and a reward to a firm that elected to resist Mr. Trump rather than, like some of its Big Law peers, cut a deal with him. The decision is expected to be appealed.

Judge Howell, an appointee of President Obama to the District of Columbia district court, writes in her 102-page decision: “No American President has ever before issued executive orders … targeting a prominent law firm.” She adds that the order “draws from a playbook as old as Shakespeare, who penned the phrase: ‘The first thing we do, let’s kill all the lawyers.’”

Mr. Trump and his legal team had anticipated the hostile ruling. In March, they filed a motion seeking to disqualify Judge Howell, writing that she “repeatedly demonstrated partiality against and animus towards the president.” Judge Howell in 2019 allowed House Democrats to view secret grand jury materials from Special Counsel Robert Mueller’s Russia investigation. Judge Howell was unmoved by the disqualification motion in this case. An appeals court has yet to rule on the matter.

In the meantime, Judge Howell’s playful use of Shakespeare jumps off the page of her opinion. The “let’s kill all the lawyers” line comes in the second scene of Act IV of “Henry VI, Part 2,” in a conversation between the rebel leader Jack Cade and his aide-de-camp , Dick the Butcher. The proposal is offered as a suggestion by which England might be improved. Judge Howell writes: “When Shakespeare’s character, a rebel leader intent on becoming king, hears this suggestion, he promptly incorporates this tactic as part of his plan to assume power.”

That same line is no stranger to judicial interpretation. Justice John Paul Stevens, in a dissent from 1985, wrote that Shakespeare’s prose surfaces the truth that “disposing of lawyers is a step in the direction of a totalitarian form of government.” Judge Howell concurs, writing that “eliminating lawyers as the guardians of the rule of law removes a major impediment to the path to more power.”

She accuses Mr. Trump of “a cringe-worthy twist on the theatrical phrase ‘Let’s kill all the lawyers,’ by instead taking the approach of ‘Let’s kill the lawyers I don’t like.’” Shakespeare’s play, while drawing on English history, is burnished by the Bard’s imagination, meaning that the line cited by Judge Howell is the playwright’s invention. On what evidence Judge Howell makes the connection is not entirely apparent. The real-life Jack Cade was not a would-be tyrant. His 1450 popular uprising was against corruption and maladministration by the king’s bureaucrats, and he was mortally wounded while fleeing in defeat.

This is not the first time that Judge Howell has displayed a literary bent. At an earlier hearing where she temporarily blocked this order, she mused: “This may be amusing in ‘Alice in Wonderland,’ where the Queen of Hearts yells, ‘Off with their heads’ at annoying subjects and announces a sentence before a verdict. But this cannot be the reality we are living under.”

The judge’s ruling is the first permanent injunction blocking Mr. Trump’s sanctioning of a law firm. He has issued a dozen such executive orders. The order against Perkins revoked security clearances for its employees, restricted their access to government buildings, and ended government contracts with the firm.

Mr. Trump’s order, “Addressing Risks From Perkins Coie LLP,” explains that “in 2016 while representing failed Presidential candidate Hillary Clinton, Perkins Coie hired Fusion GPS, which then manufactured a false ‘dossier’ designed to steal an election.” The president also contends that the Seattle-based firm, an ardent supporter of liberal causes — even as it relies on the federal government for much of its business — “has worked with activist donors including George Soros.”

One of the firm’s former partners, Marc Elias, appeared on “60 Minutes” on Sunday night to call Mr. Trump “the walking embodiment of everything that is wrong with the American political system.” It was Mr. Elias, a longtime Democratic rainmaker, who brokered the deal between Perkins and Fusion GPS, the company behind the infamous and debunked dossier compiled by Christopher Steele. In the “60 Minutes” segment, he acknowledged that Mr. Trump “hates” him.

Four firms, including Perkins, have decided to contest Mr. Trump’s orders in court. The rest have reached agreements with the administration whereby the orders were withdrawn in exchange for scaling back diversity, equity, and inclusion initiatives and setting aside pro bono funds for causes precious to the president. The Bulwark reports that these firms, though, are now arguing that they are under no obligation to take on specific clients.

Judge Howell notes that courts can only intervene when firms “make the choice to challenge rather than back down.” The judge concedes that Perkins’s “representation of President Trump’s political opponent in the 2016 presidential campaign and representation of other clients in connection with election litigation has drawn President Trump’s attention and ire.”

The judge, in granting Perkins’s motion for summary judgment, upheld the firm’s argument that Mr. Trump’s order is crosswise with the Constitution. Perkins argues that its constitutional injuries comprise denials of the freedom of speech, the right to counsel, due process, and viewpoint discrimination.

Judge Howell, a former chief justice of the District of Columbia district courts who has now taken senior status, has butted heads with Mr. Trump before. In addition to her ruling on the Mueller grand jury transcripts, she presided over many cases relating to January 6, and called the president’s rationale for pardoning nearly all of those convicted for the riot at the Capitol “flatly wrong” and “revisionist myth.”

Along with Judge James Boasberg, she’s been held up by Mr. Trump’s team as an example of judicial overreach by district-level judges blocking executive actions by the president. The question of these judges’ ability to stand athwart the presidency will be heard by the Supreme Court this spring.

WilmerHale, Susman Godfrey, and Jenner & Block are the other firms that have sued to block Mr. Trump’s executive orders against them. Perkins, in a statement released after Judge Howell’s ruling, declared that the decision “affirms core constitutional freedoms all Americans hold dear, including free speech, due process, and the right to select counsel without the fear of retribution.”